Knowing grammatical rules such as when to use commonly confused words like insure, ensure, and assure can make your writing sound more professional. Use YourDictionary's help to guide you.

When to Use Insure

Insure does relate to the buying and selling of insurance. However, people can also use it to mean "to make sure of something." While you can often substitute ensure for insure, it is most often used in relation to the insurance industry in American English. For example:

John and Jodi needed to insure their home against flood damage.

Insuring your home in anticipation of natural disasters is a good idea.

Barbara got insured after she spoke to her local agent.

When to Use Ensure

Ensure and insure can be considered synonyms because of their interchangeability. In fact, insure has a very similar definition to ensure: "to make something certain or safe." Use ensure in the following ways:

The dog owner always would ensure that he returned home quickly.

Billy was to ensure that the computer was packed safely.

He double-checked the stove to ensure it was off before leaving on vacation.

You can also use insure in any of the previous sentences (Billy was to insure that the computer was packed safely.) without changing the meaning of the sentence. While either way is technically correct, it is important to note again that insure is most frequently associated with the commercial insurance industry. In that instance, you cannot substitute ensure for insure.

When to Use Assure

Just like insure and ensure, assure means "to make a statement for the purpose of inspiring morale or belief in someone or to make someone confident in their beliefs and ideas." However, only assure is used "with reference to a person in the sense of 'to make someone confident.'" To illustrate this, consider the following examples:

Suzanne assured Robby that his report to the board was excellent.

Kelly was head over heels for Bill, but she did not feel assured that he felt the same way.

When his mom picked him up, the baby was assured she was there for him.

Three Helpful Hints

Knowing the meaning of insure, ensure, and assure does not help differentiate among the three words, because they all have the same definition. Despite that, they cannot always be used interchangeably.

To help you remember when to use each word, keep the following three hints in mind:

• You assure a person.

• You insure your car.

• You ensure everything else.

Again, it is okay to swap ensure for insure unless it relates to protecting people or property against risks like floods, death, hurricanes, and the like. Assure cannot be used in place of either insure or ensure, and is the only word which should be used to relate to a person's feelings.

Differing Opinions from Differing Resources

Despite the fact that insure can be used for ensure, and vice versa (unless relating to the actual insurance business), this does not mean that all writing sources agree on the proper use. For example, the Associated Press notes that insure should be used only when relating to financial manners. It does not state that ensure and insure are "generally interchangeable."

With this noted, it is important to find out from your employer or professor which style he/she would prefer that you write in. While it is permissible to exchange ensure and insure, common sense would dictate that insure relates to the business, ensure refers to securing an action, and assure relates to easing a person's mind.

Practice Makes Perfect

If you are still not clear on when to use insure, ensure, and assure, you are not alone. Practice makes perfect, so try to figure out which belongs in the following sentences. Answers are given in the final paragraph.

Jimmy needed to __________ that his safe was properly locked.

Sara ________ed her motorcycle before she rode it.

No matter how bad you feel about your breakup, you can be __________ed by the fact that your ex feels even worse.

__________ your son that his piano playing sounds wonderful.

__________ that your daughter practices her dance routine.

The correct answer to sentence one is "ensure," because Jimmy needed to make certain that his safe was locked. The correct answer to sentence two is "insure," because it relates to the commercial industry of money and risk taking. Sentence three's answer is "assure," because it eases your mind to know your ex feels worse. Sentence four's answer is "assure," because you are easing your son's mind regarding his abilities. The correct answer to sentence five is "ensure," because you are making certain your daughter practices her dance routine.